so ive been running an RTL-SDR v3 for about two years now, mostly just listening to NOAA weather sats, some ADS-B, poking around the local repeaters and whatnot. works fine for that stuff but ive been wanting to get into some things that need a bit more dynamic range and the RTL just doesnt cut it once you get near a strong local broadcast station or a big pager system nearby.

been looking at either the SDRplay RSPdx or a HackRF One. i know theyre kind of different beasts - HackRF can transmit which is cool but the noise figure is pretty terrible compared to the RSPdx if i remember right. something like 8-10dB on the HackRF vs like 3-4 on the RSP. for receive-only monitoring does that actually matter in practice or is it one of those spec sheet things that doesnt translate much to real world use.

mostly want to do better HF monitoring, maybe some satellite stuff, decoding some digital modes. not really interested in transmitting with it. budget is flexible but id rather not spend $300+ if the RSPdx isnt meaningfully better than just grabbing a good upconverter for the RTL dongle i already have.

went through this exact decision about a year ago. ended up with the RSPdx and honestly no regrets. the noise figure thing does matter on HF especially if youre not in an RF-rich urban environment where everything is loud anyway. tried a friends HackRF at a hamfest and the receive sensitivity difference on 40m was pretty noticeable - not night and day but enough that it would bug me. the SDRuno software that comes with the RSPdx is pretty decent too once you get past the initial setup which is a little quirky. if you just want to receive and do it well the RSPdx is hard to argue against at that price point. the upconverter route with your existing dongle is fine but youre still bottlenecked by the RTLs ADC which is what really limits the dynamic range, not just the frequency coverage.

i have both actually and use them for different things. HackRF lives on my bench for RF experiments and portapack stuff, RSPdx is hooked to a long wire for HF monitoring. they really arent competing for the same job in my setup. that said if i had to pick just one for what you described id go RSP without hesitating. SDRuno can be a bit clunky but SDRplay has been solid on driver support across Windows and linux which matters if you ever switch. also worth looking at SDR++ if you havent, works great with basically everything and a lot cleaner than SDRuno for just monitoring.